Head mounted or otherwise wearable image projection system for projecting virtual and/or augmented virtual reality to the user eye(s) are becoming increasingly popular. Such systems are in many cases configured as glasses mountable onto a use's head and operable for projecting images to the user's eyes for providing virtual reality image/video projection to the user. To this end, certain of the known systems are aimed at providing pure virtual reality image projections to the user eyes, in which light from the external scenery is blocked from reaching the eye(s), while other systems are directed to provide augmented virtual reality perception, in which the light from the external scenery is allowed to pass to the eyes, while also being augmented/superposed by images/video frames projected to the eyes by the image projection systems.
For example, U.S. patent application No. 2013044042 discloses an electronic device including a frame configured to be worn on the head of a user. The frame can include a bridge configured to be supported on the nose of the user and a brow portion coupled to and extending away from the bridge and configured to be positioned over a side of a brow of the user. The frame can further include an arm coupled to the brow portion and extending to a free end. The first arm can be positionable over a temple of the user with the free end disposed near an ear of the user. The device can also include a transparent display affixed to the frame adjacent the brow portion and an input affixed to the frame and configured for receiving from the user an input associated with a function. Information related to the function can be presentable on the display.
U.S. Pat. No. 7,936,519 disclosed a head mounted display including: an eyeglasses frame-like frame to be mounted onto an observer's head; and two image display devices, each of the image display devices including an image generating device, and light guide means which is mounted to the image generating device, which as a whole is located on the side of the center of an observer's face relative to the image generating device, on which beams emitted from the image generating device are incident, through which the beams are guided, and from which the beams are emitted toward an observer's pupil.
U.S. Pat. No. 8,289,231 discloses a head mounted virtual image display unit which is compact in size and weight, and incorporates a high performance optical system offering a clear see-through capability. A sliding light shield may be incorporated for those instances when see-through capability is not desired. A focus adjustment may be incorporated to permit the focusing of the image, for example, at a distance of approximately 18 inches to infinity. An adjustable headband may be incorporated that adapts to fit the users head. A flexible boom structure may be incorporated to facilitate fine positional adjustment of the optical assembly. A slider and ball joint mechanism may also be incorporated to facilitate positional adjustment of the optical assembly. A built-in microphone may be incorporated to enable speech input by the user. The head mounted virtual image display unit may be used comfortably in conjunction with eye or safety glasses, and provides a useful image to the user without blocking his view of the surrounding environment. The unit is designed to have a pleasing appearance so as to greatly enhance user acceptability.
U.S. Pat. No. 8,384,999 disclosing an optical module for head mounted displays and other applications. The optical module includes an optical substrate and optical superstrate having inter-engaging ridged surfaces. A reflective layer is formed on at least one of the surfaces. An index matching material may be located between the surfaces. A region that receives a projected image, from a projector, directs rays launched from the projector onto the ridged surfaces, so that in use a viewer perceives an augmented image. The augmented image includes reflected rays from the projector and transmitted rays from an object located on an opposite side of the module to that of the viewer.
In certain techniques eye position and movement are tracked to determine a focal region for the user. A technique tracking gaze is disclosed for example in U.S. Pat. No. 6,943,754.
U.S. patent application No. 2012154277 discloses a method and system that enhances a user's experience when using a near eye display device, such as a see-through display device or a head mounted display device is provided. An optimized image for display relative to a field of view of a user in a scene is created. The user's head and eye position and movement are tracked to determine a focal region for the user. A portion of the optimized image is coupled to the user's focal region in the current position of the eyes, a next position of the head and eyes predicted, and a portion of the optimized image coupled to the user's focal region in the next position.
U.S. Pat. No. 7,542,210 discloses a head mounted display device having a mount which attaches the device to a user's head, a beam-splitter attached to the mount with movement devices, an image projector which projects images onto the beam-splitter, an eye-tracker which tracks a user's eye's gaze, and one or more processors. The device uses the eye tracker and movement devices, along with an optional head-tracker, to move the beam-splitter about the center of the eye's rotation, keeping the beam-splitter in the eye's direct line-of-sight. The user simultaneously views the image and the environment behind the image. A second beam-splitter, eye-tracker, and projector can be used on the user's other eye to create a stereoptic, virtual environment. The display can correspond to the resolving power of the human eye. The invention presets a high-resolution image wherever the user looks.
International patent application publication No. WO 2013/117999 discloses systems, methods and computer program products for gaze tracking. An exemplary method includes directing light into an eye using a projector; detecting, using an image-capturing module, a reflection from a surface associated with the eye; and determining a line of sight associated with the eye based on the detected reflection. In some embodiments, the light comprises infra-red light. In some embodiments, the projector comprises a laser. In some embodiments, the projector comprises a liquid crystal on silicon (LCoS) chip. In some embodiments, the surface associated with the reflection is at least one of the cornea, the iris, or the retina.